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TypeScript Fundamentals

Core TypeScript concepts for Java developers transitioning to web development. Start here if you're new to TypeScript.

A Brief History

JavaScript: 10 Days That Changed the Web

JavaScript was created in 1995 by Brendan Eich at Netscape Communications — famously in just 10 days. Originally called Mocha, then LiveScript, it was renamed JavaScript as a marketing play to ride Java's popularity (despite having almost nothing in common with Java beyond curly braces).

The early web needed client-side interactivity. Before JavaScript, every user action required a full page reload from the server. JavaScript changed that — form validation, dynamic content, and responsive interfaces became possible without round-trips.

JavaScript grew fast. The language was standardized as ECMAScript in 1997, and major versions followed:

Version Year Key Additions
ES5 2009 strict mode, JSON, array methods (forEach, map, filter)
ES6/ES2015 2015 let/const, arrow functions, classes, Promises, modules
ES2017 2017 async/await
ES2020 2020 Optional chaining (?.), nullish coalescing (??)

In 2009, Ryan Dahl created Node.js, bringing JavaScript to the server. Suddenly one language could power both the browser and the back end. The Node.js ecosystem exploded — npm now hosts over 2 million packages, and JavaScript consistently ranks as the most-used programming language in developer surveys.

TypeScript: JavaScript That Scales

By the early 2010s, JavaScript was being used to build large, complex applications — but the language's dynamic typing made it hard to catch bugs early, refactor safely, or navigate large codebases. Microsoft saw the problem and in 2012, Anders Hejlsberg (the creator of C# and Turbo Pascal) released TypeScript.

TypeScript is a superset of JavaScript — every valid JavaScript program is also a valid TypeScript program. TypeScript adds:

  • Static type annotations — catch type errors at compile time, not runtime
  • Interfaces and type aliases — describe the shape of data
  • Generics — write reusable, type-safe code
  • IDE support — autocomplete, inline errors, and safe refactoring

TypeScript compiles down to plain JavaScript — the browser and Node.js never see the types. This means you get the safety of a typed language during development with zero runtime cost.

Adoption has been massive. As of 2024, TypeScript is used by:

  • Microsoft — VS Code, Azure, Office 365
  • Google — Angular (built in TypeScript from the start)
  • Airbnb, Slack, Stripe, Shopify — large-scale web applications
  • Every major framework — React, Next.js, Express, Prisma all have first-class TypeScript support

Why TypeScript for TCSS 460?

You already know Java — a statically typed, object-oriented language. TypeScript bridges the gap:

Concept Java TypeScript
Type system Static, nominal Static, structural
Compilation javac → bytecode → JVM tsc → JavaScript → Node.js/browser
Null safety NullPointerException at runtime strictNullChecks at compile time
Interfaces implements keyword Structural ("duck typing")
Generics List<String> Array<string>
Package manager Maven/Gradle npm
Build tool javac/Maven tsc/esbuild/SWC

TypeScript gives you the type safety you're used to from Java, while introducing you to the JavaScript ecosystem that powers modern web development. In this course, every project — from the Express API to the Next.js front end — is written in TypeScript.

Sources and Further Reading

Guides

These guides are your reference throughout the quarter. Start with the Fundamentals, then explore Async and Tools as needed.

Fundamentals

The core language — types, functions, objects, modules, and array methods. Work through these in order during Week 1.

Async Programming

JavaScript is asynchronous by nature. These guides cover the patterns you'll use constantly in Express and Next.js.

Tools

Your development environment and AI coding assistants.